The design of fully differential CMOS operational amplifiers without extra common-mode feedback circuits

P. H. Lu*, Chung-Yu Wu, M. K. Tsai

*Corresponding author for this work

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

A new fully differential CMOS operational amplifier (op amp) without extra common-mode feedback (CMFB) circuit is proposed and analyzed. In this op amp, simple inversely connected current-mirror pairs are used as active loads. From the theoretical analysis, it is shown that the common-mode signal can be efficiently suppressed by the reduced effective common-mode resistance of the active load. The proposed op amp with 2 pF capacitance loadings has an open-loop unity-gain bandwidth of 63 MHz, a phase margin 47°, and a dc gain of 67 dB in 3.5 μm p-well CMOS technology. The common-mode gain at a single output node can be as low as -38 dB without extra CMFB circuit. Experimental results have successfully confirmed the capability of the efficient common-mode rejection.

Original languageEnglish
Pages (from-to)173-186
Number of pages14
JournalAnalog Integrated Circuits and Signal Processing
Volume4
Issue number2
DOIs
StatePublished - 1 Sep 1993

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